1.4.8 Explain the mechanism of action and specificity of enzymes in terms of their three-dimensional structure and explain that enzymes are biological catalysts that reduce activation energy, catalysing a wide range of intracellular and extracellular reactions.

- Enzymes are biological catalysts that speed up reaction both inside cells (intracellular) and out side cells (extracellular) by lowering the activation energy.

- Enzymes are globular proteins and each enzyme has a specific 3D shape including an active site. 

- Only substrates with a specific shape fit into the active site. 

- This close interaction of the complementary-shaped enzyme substate is known as the lock and key hypothesis. 

- The substrate may induce the enzyme to the right shape. This is called the induced fit theory.